Rate of glucose utilization, as measured by a new autoradiographic technique, normally varies from region to region in the fetal sheep brain in utero with differential increases in rates as gestation progresses, followed by an abrupt increase in some structures at birth. Preliminary experimental work suggests a relationship between rate of local cerebral energy metabolism and behavioral states of the fetal and newborn sheep. In the present experiments, behavioral states of arousal, quiet sleep and rapid eye movement sleep will be scored on the basis of desynchronized or synchronized electrocorticogram, random, slow, absent or conjugate eye movements, and tone or atonia of neck muscles. Behavioral state will be correlated with rate of local cerebral glucose utilization as measured by a quantitative autoradiographic technique using (C14) deoxyglucose as the labelled tracer for glucose. The method allows the determination of glucose utilization simultaneously in all structural and functional parts of the brain. Fetal and newborn heart rate, blood pressure, blood p02 and pCO2, and blood pH will be measured also. In a second group of experiments, local cerebral glucose utilization of fetal and newborn sheep will be measured during acoustic and vestibular stimulation. Fetal behavioral state, heart rate, blood pressure and blood gases will be assessed. The study of the connection between behavioral state and cerebral metabolism, both in basal states and in adaptive responses to well-defined stimuli, may be critical to an understanding of normal brain development and the mechanism of arousal in the newborn.